Electrodeposition of metals



Patented Dec. 22, 1936 Northwest Chemical 00., Inc., Detroit, Mich., corporation of Michigan g. Application July 19, 1934,

No Drawin Serial N 736,047

sTA'ras PATENT OFFICE ELECTRODEPOSITION OF METALS Bernard F. Lewis, Detroit, Mich., asslgnoflto 1 Claim.

' of metals and more particularly to the electrodepositing of copper.

In the practice of this art in the past, and

particularly with respect to copper, both alkaline and acid baths have been employed. Inthe acid bath the deposit was of a crystalline character. In the alkaline bath, while a more satisfactory deposit was obtained, the coating of copper deposited was frequently rough, porous and dull and necessitated an expensive buffing operation to render it suitable for the application of a finish coating. A number of explanations were advanced for these disadvantages, including an undesirable combination of constituents in the bath and the activity of the gaseous bubble formation of hydrogen at the cathode tending to produce relatively porous plating. Whatever the cause may be an object of my invention is to produce a coating of electrodeposited copper which is smooth, dense and lustrous and to accomplish this result at low cost.

I have found that very smooth, dense, semilustrous deposits of copper may be produced from an alkaline electrolyte containing a combination of ingredients within certain prescribed limits, employed under certain prescribed conditions, and in which there is present an inorganic colloid such as aluminum hydroxide or sodium 30 l aluminate.

A bath fumishing the above noted results may be prepared by dissolving in water, carbonate of copper, cyanide of copper, copper oxide, or other copper compound, in just sufficient alkali cyanide solution to form the double copper cyanide. To

this solution of double copper cyanide there is added aluminum, either as a metal, or any compound of aluminum which is soluble in the bath;

a base forming substance; a salt of an'organic acid other thana cyanide; and there may be added an alkali cyanide; and a salt containing a sulphate radical.

An electrolytic bath which has produced very desirable results is given in a table herebelow.

The table indicates the operable range of concentrations and a preferred concentration of the various constituents expressed in ounces per chemical equivalent in mother alkali).

0.25%01-0001 gal This invention relates to the electrodeposition The manner of efiecting a solution of these constituents is not important; nor is there any limitation as to the chemical compound from which the metals or radicals are derived.

The presence of the inorganic colloid, such as 5 aluminum or other suitable metal of the same group, in the electrolytic bath functions to pro-' duce a dense, smooth,'hard, and lustrous deposit of copper free from the porosities and spongy characteristics which result when the colloid is omitted. It is not my intention to limit my claim to the electrcdepositing of copper.. The invention is also applicable to other alkaline electrolytic baths wherein metal is deposited.

Other factors also apparently enter into the production of my improved plating. The ingredients employed as well as their proportions with respect to one another are important. Attention is directed to the fact that the concentrations of the ingredients are relatively low per gallon of electrolyte. The low concentration of the constituents of the bath and their relative pro portions assist materially in producing my improved metal plating. v

The temperature of the bath may be that generally provided for in the art- Atemperature range of between 120 and 160 Fahrenheit has been found to give good results. I,

The ingredients noted above may be prepared and mixed in dry form, either with or without the metal to be such condition;

What I claim is:

An electroplating bath for electrodepositing deposited, and marketed under 'copper containing the following substances in substantially the proportions named: '.10 to .50 ounce of copper; .25 ounce of free alkali cyanide; .90 ounce of sodium citrate or other salt having the citrate radical; .007 ounce of aluminum or of ametal of the same group; .25 ounce of sulphate 40 compounds; .50 ounce of sodium hydroxide or its chemical equivalent, in 1 'gallon of water.

BERNARD F. LEWIS. 

